System of electrical distribution.



No. 784,328. PATENTED MAR. '7. 1905.

F. HOFFMAN.

SYSTEM OF ELECTRICAL DISTRIBUTION APPLICATION FILED MAY 21, 1903.

2 SHEETS-SHEET 1.

PATENTED MAR. 7. 1905.

I. HOFFMAN.

SYSTEM OF ELECTRICAL DISTRIBUTION.

APPLICATION FILED MAY 21, 1903.

2 SHEETSSHEET 2,

.ZZQ ZZ 561? (Z77,

UNITED STATES Patented March 7, 1905.

PATENT OFFICE.

FRANK HOFFMAN, OF CHICAGO, ILLINOIS. ASSIGNOR OF ONE-HALF TO ELMER E.HANNA, OF CHICAGO, ILLINOIS.

SYSTEM OF ELECTRICAL DISTRIBUTION.

SPECIFICATION forming part of Letters Patent N0. 784,328, dated March'7, 1905.

I Application filed May 21,1903. Serial No. 153,101.

To all wh/mn it may concern:

Be it known that I, FRANK HorFMAN, a citizen of the United States.residing at Chicago, in the county of Cook and State of Illinois,

have invented certain new and useful Improvementsin Systems ofElectrical Distribution, of which the following is a specification.

An application filed by me August 13, 1903, Serial No. 169,310, Systemof electrical distribution, is a division of this application, andsubject-matter described, but not claimed herein, will be founddescribed and claimed in said divisional application.

This invention relates to a method of electrical distribution having forits principal object the providing of a simple, economical, .andefiicient method by which an electric motor or motors may be suppliedwith current so as to obtain substantially uniform speed or change ofspeed to meet different circumstances and conditions, as will more fullyhereinafter appear.

The principal object of the invention is to provide a method ofobtaining a change of speed of electric motors whereby three or morecircuits of substantially equal potential are maintained and the motorsconnected therewith, so that all circuits which are simultaneously inoperation carry substantially equal loads.

The invention consists principally in a method of obtaining uniform orchange of speed in an electric motor which consists in maintaining threeor more circuits of equal potential and connecting thearmature-terminals of an electric motor with different pairs ofconductors on said circuits, as desired.

In practicing the invention I employ a system of electrical distributionin which there 4 are combined a plurality of generators of equalelectric force and capacity, a plurality of electric conductors formingthree or more electric circuits of equal potential and con necting theopposite poles of said generators in series, an electric motor, andswitch-mechanism connecting the electric motor with different pairs ofthe conductors.

The invention consists, further and finally,in

the features, combinations, and details of construction hereinafterdescribed and claimed. 5

In the accompanying drawings, Figurel is a diagram of a system embodyingone form of my improven'ients; and Fig. 2, a diagram embodying amodification thereof, as will more fully hereinafter appear.

In the art to which this invention relates it is well known that it isvery desirable to so arrange the wiring and distribution of the electricenergy that each circuit or pair of wires and the generator furnishingthe cur- 6O rent thereto should have as nearly as possible a constantload and each circuit a load equal with the others or be in balance, sothat the motors may be run at uniform speeds or at different speedswithout destroying the bal- 5 ance of the system.

Describing first the system illustrated in Fig 1, a is a main generatorof the desired electromotive force and capacity of developing, forinstance, two hundred and twenty 7 volts and is connected with fourmotor-generators b, 7), b and I) by means of the main lead-wires 1 and2. These supplementary or motor generators, as I prefer to term them,are connected across the main leads in the series and have theiropposite poles connected in series with a plurality of conductors 3, 4,and 5 and the main conductors 1 and 2 above described, so as to formthree or more circuits of equal potential. These motor-generators are ofsuchconstruction that they develop when running at speed anelectromotive force of fifty-five volts each, so that it will be seenthat the circuit formed between any pair of adjacent conductors has apotential of Iifty- 5 five volts, while between any other pair therewould be a multiple thereof say, for instance, between 1 and t therewould be a circuit having a potential of one hundred and ten volts,between 1 and 5 a circuit having a potential 9 of one hundred andsixty-five volts, and between 1 and 2 a circuit having the maximumpotential of two hundred and twenty volts.

In this h'gure I have shown three electric motors c, (l, and a, allconnected between the above-named conductors, so that the desired out ofbalance by any of these changes.

speeds may be obtained. One armature-terminal of the electric motor 0 isconnected with the main lead 2 by means of the wire 6 and its oppositeterminal by means of wire 7, and switch-lever 8 may be connected withany of the contact-points 9, 10, 11, or 12 of the other Wires. 1n thedrawings it is connected with the contact-point 12 of Wire 5 and istherefore in a circuit formed by wires 2 and 5, having a potential offifty-five volts. One armature-terminal of the electric motor (Z isconnected with the main lead 1 by means of wire 14 and its oppositeterminal by means of the wire 15, and the switch-lever 16 is connectedwith the contact-point 11 of wire 4:, so that such motor is in thecircuit formed by wires 1 and 1 and has a potential of twice fifty-fivevolts viz., one hundred and ten volts. The armattire-terminals of theelectric motor 6 are by means of wires 17 and 18 connected with the mainwires 1 and 2 and are embraced in the circuit having the maximumpotential on the multiple of four circuits viz., two hundred and twentyvolts.

From the above description and an examination of Fig. 1 it will be seenthat either of the electric motors 0 and (Z can be placed in a circuithaving a potential of fifty-five volts or the multiple thereofsuch asone hundred and ten, one hundred and sixty-five, or two hundred andtwenty volts whenever occasion requires and that the system will not bethrown In other Words, both motors cannot come at one time on wires 1and 3, 4: or 5, nor on 2 and 5, 4 or 3, and any number of motors can bearranged in the same way also. The lowest voltage may be taken betweenthe wires 3 and 4, 4 and 5, and the other voltagessay one hundred andtenbetween wires 3 and 5, as well as between 1 and 1 or 2 and 1, thusenabling all the generators and wires to be of one size and capacity andmuch smaller than where the lowest voltage can come from one generatorand on two wires only.

In Fig. 2 I have illustrated the prime mover as a steam-engine 0 insteadof an electric generator, as shown in Fig. 1. This steamengine, by meansof a belt it, drives an armature-shaft 2', carrying four electricgenerators i, f, 2'", and 71*, the opposite poles of which are connectedin series with a plurality of conductors 20, 21, 22, 23,and 24;, so asto form four electric circuits of equal potential. These electricgenerators are of the same electromotive force and capacity-say aboutfifty-live voltsso that each independent circuit has a potential offifty-live volts; but when wires of different pairs are connected acrossin any desired manner a circuit of different potential than any of thegenerators, but a multiple thereof, may be obtainedin other words, a

circuit of the potential of all the generators combined or of two ormore. An electric motor Z; is provided, the armature-terminals of whichare connected with switch-levers 25 and 26 by means of wires 27 and 28,respectively. These switch-levers are so arranged that the motor X: maybe thrown into a circuit formed by any two pairs of the conductors. Asshown in the drawings, it is electrically connected with the conductors21 and 23, so as to form a circuit having the potential ol two circuitswith a total potential of one hundred and ten volts. A switch-lever,however, may be thrown into electric connection with any of thecontact-points 29, 30, 31, 32, and 33 and obtain any potential forcewhich is the multiple of fifty-live. For instance, the switch-lever 25may be moved over so as to contact the point 29, and thereby embrace acircuit formed by the pairs of wires 20 and 23, having a potential threetimes fifty-live volts namely, one hundred-and sixty-live volts.

From the foregoing description of construction and operation it will beseen that any one of the motors in either figure, with the exception ofthe motor a, may be switched from any single pair to any other pair ofconductors for obtaining the uniform speed, or it may be connected withany other given pair to obtain a change of speed or embraced in theelectric circuit which has a potential equal to the sum of the potentialof the several circuits.

The principal advantage resulting from the use of my improvements is, asabove stated, the possibility of using when operating a plurality ofmotors the minimum potential, maximum potential, or any intermediatepotential without disturbing the balance of the system.

I claim-- 1. The herein-described method of obtaining a uniform orchange of speed of an elec tric motor, which consists in maintainingthree or more circuits of equal potential and connecting thearmature-terminals of a motor with difi erent pairs of conductors onsaid circuits, so that all circuits which are simultaneously inoperation carry substantially equal loads, substantially as described.

2. The method of obtaining a change 01 speed of electric motors whichconsists in maintaining three or more electric circuits of substantiallyequal potential and connecting a plurality of motors therewith, so thatall circuits which are simultaneously in operation carry substantiallyequal loads, substantially as described.

FRANK HOFFMAN.

\Vitnesses:

Emma E. HANNA, THOMAS F. SHERIDAN.

